The present invention relates to an improved powder feed device for a powder dispensing apparatus such as a manual or automatic electrostatic powder spray gun.
The present invention relates more particularly to a powder feed device of the type in which the feeding of powder to the powder dispensing apparatus is effected pneumatically through a flexible tube or hose having an internal diameter of the order of 12 millimeters (about a half an inch), for example, by connecting the inlet of the dispensing apparatus to a powder fluidization tank through venturi extracting means.
The pneumatic transportation through such a tube or hose which may be several meters long, generally requires very high air flow rates if concentrations or clumps of the transported powder are to be avoided, by maintaining a relatively homogeneous powder suspension in the entraining air. Such high air flow rates mean air flow speeds greater than 8 m/s which are deleterious to electrostatic spraying as the trajectories of powder particles are unduly influenced by their velocity as opposed to the electrostatic field.